Energy and environmental protection are topics of 21th century, and China has been the first energy source-importing country in the world at present. Environmental problems such as fog, haze, and the like accompanying with consumption of fossil energy sources gradually become severe, and it is urgently required to seek clean and sustainable energy sources. The development and use of solar energy, which is a kind of renewable and clean energy source, is one of hot spots in the research area of energy sources.
Much attention has been paid to the dye-sensitized solar cell world widely, which is an important type of solar cells. In 1991, a research team of Grätzel produced a device by adsorbing a trinuclear ruthenium dye RuL2(μ-(CN)Ru(CN)L′2)2 (L is 2,2′-bipyridin-4,4′-dicarboxylic acid, L′=2,2′-bipyridine) reported by Amadelli et al. on a high-quality TiO2 nanocrystal which was developed by them in several years. A power conversion efficiency of 7.1% was achieved under simulated sunlight, and the research on dye-sensitized solar cells was thereby started. Compared to conventional inorganic semiconductor solar cells, dye-sensitized solar cells have relatively low-cost of production, abundant colors, and good appearance, and may be produced into semitransparent products. Flexible dye-sensitized solar cells can be widely used in daily life due to their relatively lightweight, foldable and windable properties.
At present, dyes used in commercial solar cells are all ruthenium complexes containing the precious metal. However, the resource of ruthenium is insufficient, and the cost of ruthenium-based materials is high, which severely impedes their productions and applications in a large scale, and thereby pure organic dyes have been the general trend. However, only few devices can achieve a power conversion efficiency over 10% produced with pure organic dyes at present. In addition, the complicated synthesis of most of the materials used in high efficient devices hinders the development of the pure organic dyes in dye sensitized solar cells. Furthermore, there are few highly efficient blue dyes, and thus the universality and practicability in application are limited.